configure.py: Compile protobuf files
configure.py: Compile protobuf files

This adds the relevant rules to configure.py to compile protobuf files.
Currently the only file that is being compiled is the metric for
prometheus.

Signed-off-by: Amnon Heiman <ed5fc74c4692051ad0b19749fd7cea6ec2d74b9e@scylladb.com>

avikivity/seastar,kjniemi/seastar,cloudius-systems/seastar,scylladb/seastar,scylladb/seastar,scylladb/seastar,dreamsxin/seastar,syuu1228/seastar,syuu1228/seastar,syuu1228/seastar,dreamsxin/seastar,dreamsxin/seastar,kjniemi/seastar,avikivity/seastar,avikivity/seastar,cloudius-systems/seastar,cloudius-systems/seastar,kjniemi/seastar